1. Field of the Invention
The present invention relates to a discharging device, and more particularly to a discharging device for a caulking gun and having a ratchet push rod that will automatically move backward before the ratchet push rod is engaged with a pawl. The backward movement of the ratchet push rod prevents the continuous discharge of caulking material when a discharging operation is halted.
2. Description of Related Art
Caulking guns are widely used to fill spaces between pieces of wood or glass on a boat or around edges of windows with a special material such as silicon or caulking that keeps water out. A conventional discharging device for a caulking gun includes a body with a front end and a rear end. A handle is attached to the rear end of the body, and a ratchet push rod with a series of teeth passes through the body from the rear end to the front end. A trigger is attached to the body to repeatedly push the ratchet push rod forward to discharge caulking material such as silicon from a tube. A pawl is attached to the rear end of the body to prevent the ratchet push rod from being pushed back.
However, the conventional discharging device for a caulking gun only forces the ratchet push rod in one direction. Furthermore, when the caulking material in the tube is exhausted, the ratchet push rod must be rotated 180 degrees so the teeth of the ratchet push rod separate from the pawl. Thus, the ratchet push rod can be pulled back so the tube of caulking material can be replaced.
The conventional discharging device for a caulking gun has the following shortcomings.
First, when a discharging operation is halted, pressure remains on the caulking material in the tube, and the pressure is higher than ambient air pressure. Because of the two pressures are not equal, the caulking material such as silicon in the tube will continue to be discharged from the tube until the pressure in the tube is equal to the ambient air pressure.
Second, when users replace the tube, the ratchet push rod must be rotated to displace the teeth of the ratchet push rod away from the trigger and the pawl. However, the trigger and the pawl still press against the ratchet push rod, which will damage the ratchet push rod because friction is generated between the push rod and the trigger and the pawl.
The conventional discharging device moves the ratchet push rod a forward distance three to four times the pitch between the teeth of the ratchet push rod. The conventional discharging device only allows a very small backward movement of the ratchet push rod. The distance is not enough to relieve the residual pressure in the tube and equalize the internal pressure with the ambient air pressure so the material in the tube will continue to be discharged when the discharging operation is halted.
To overcome the shortcomings, the present invention provides an improved discharging device for a caulking gun with a ratchet push rod to mitigate and/or obviate the aforementioned problems.
The main objective of the invention is to provide an improved discharging device for a caulking gun with a ratchet push rod where the discharging device can prevent the discharge of caulking material when the discharging operation is halted.